These inventions relate to a device for controlling the flow of liquid and gas at a wellhead; and more particularly to such devices for controlling the flow of a mixture of a very high temperature liquid and highly toxic gases, and which devices are operative under climatic conditions ranging from sub-zero winters to hot summers.
The flow control devices of these inventions are designed for use under particularly severe conditions encountered, for example, where the device is used for oil production from a formation of asphaltic crude which includes highly toxic gases such as hydrogen sulphide. Hydrogen sulphide is lethal when released to the atmosphere even in small quantities. The safety codes concerned with the production of crude under these highly toxic conditions are stringent; and this invention is concerned with the problem of meeting the requirements of such codes. Another problem encountered in the production of asphaltic crude, is that steam flooding production techniques may be used, wherein the superheated steam injected into the oil producing zone produces very high operating temperatures. The temperatures may be so high as to preclude the use, as packing materials, of known elastomeric materials such as fluoro-elastomers and fluoro-silicones. The flow control devices operative under these conditions must be effective to control the production flow and also prevent the release of toxic gases at these high operating temperatures. The steam flooding techniques produce very high operating pressures at the wellhead, when the flow control valve is closed, and the control devices must be capable of sealing the wellhead against such pressures.
One object of this invention is to provide a wellhead control device for controlling the flow of crude oil containing highly toxic gases such as hydrogen sulphide, and to prevent the release of such gases to the atmosphere.
Another object of this invention is to provide a wellhead control device for controlling the flow of asphaltic crude oil having hydrogen sulphide in the formation producing zone.
A further object of this invention is to provide a wellhead control device for controlling the flow of crude oil from a formation which has been steam flooded.
Still another object of this invention is to provide a wellhead flow control device for association with the polished rod of a well pump sucker rod string, the device having effective packings preventing the escape of toxic gas to the atmosphere, and which packings may be maintained and replaced with the polished rod in place.
A further object of this invention is to provide such wellhead flow control device for association with the polished rod of a well pump and having effective packings for preventing escape of toxic gas, including a leak safety shutdown for the polished rod packing.
A still further object of this invention is to provide a wellhead valve for shutting off the flow of very high viscosity crude oil, and for reopening such valve against the resistance of such very high viscosity crude oil.
Another object of this invention is to provide a wellhead flow control device for the controlling of crude oil containing toxic gas, and which device would meet the safety codes governing the operation of such devices.
These objects are accomplished in a wellhead control device including a valve and associated packing glands, configured for coaxial association with the polished rod on the well pump. The valve comprises a body providing an annular closure seat and a coacting closure ram guided for reciprocating movement relative to the closure seat. The closure ram comprises an elongated body having an axial bore dimensioned for free passage of the rod string, a compressible annular packing mounted at the closure end of the ram body, and annular retaining means for axially retaining the packing to the ram body. The closure seat comprises an annular shoulder confronting the retaining means of the ram, and a generally cylindrical wall extending from the seat shoulder toward the ram. An operator means effects reciprocation of the closure ram relative to the valve body.
More particularly the control device includes a ram packing gland, operative between the valve body and the closure ram, and a polished rod packing gland, operative between the closure ram and the pump polished rod, both effective to prevent the escape of toxic gas from the wellhead.
Still more particularly, the control device includes a polished rod packing assembly provided with a positive shutdown, to seal the polished rod in the event of leakage at the polished rod gland.
The novel features and the advantages of the invention, as well as additional objects thereof, will be understood more fully from the following description when read in connection with the accompanying drawings.